Abstract
This paper describes the results of an investigative case study to identify the causes of productivity decline in an oil well and a successful chemical treatment to restore productivity.
A well in Minami Kuwayama oil field has suffered from a significant productivity decline from the beginning of commercial production. Pressure build up tests have shown the presence of formation damage becoming larger as production goes. Then we considered the possibility of asphaltene deposition, which has been observed in most of the surface facilities, in the near wellbore formation restricting flow capacity around the well.
A multidisciplinary team was organized, with field operation engineers and researchers from the R&D center, to investigate the asphaltene behavior in the formation and to find the effective way of chemical treatment as asphaltene-control measures.
Laboratory analyses using bottom-hole fluid samples have built the onset pressure curve of asphaltene precipitation, which indicated the asphaltene deposition in the near wellbore region under the production conditions.
Then the intensive laboratory tests have been carried out to evaluate some commercial additives in terms of their efficiency as an asphaltene inhibitor under the formation conditions and to find the most effective chemical to resolve precipitated asphaltene.
Based on laboratory analyses and tests, a complete chemical treatment program consisting of injection of xylene into the formation with a three feet treatment radius and squeezing of an asphaltene inhibitor around the well has been designed and applied to the well.
This chemical treatment resulted in a significant improvement in the productivity index which is almost ten times larger comparing as before.
